In recent years, such technique that detailed information of objects existing around a user (referred to below as collateral information) is acquired in a state that the user wears a wearable display such as a head mount display (HMD) on which a camera for acquiring external information is mounted has been developed along with development of information communication technology. Collateral information includes information which does not appear superficially on an object such as information of a specific name of the object, environments in which the object is manufactured, other users' reputation with respect to the object, and the like as well as information which is obtained from an appearance of the object.
Here, when a user selects and acquires information which is desired to acquired, for example, from a plurality of pieces of collateral information, an input system of information from the user has to be prepared. In this case, an interface of related art such as a mouse and a keyboard may be used, but a method in which a motion (gesture) of a user is used as an input system has attracted attention as a simple and effective input method.
As methods in which a gesture of a user is used as an input system, a method in which a finger motion is measured with an acceleration sensor and a method in which movement of a visual line is measured with a visual line detection device which is mounted on a wearable device have been disclosed (for example, Japanese Laid-open Patent Publication No. 10-214306).
Further, to realize a hands-free or eyes-free user interface using gestures, such method that movement of a head (including a jaw) is recognized as a gesture has attracted attention, as well. Regarding a recognition method by a motion of a head, it is possible to realize natural gesture input which is related to actual daily performance of a human such as nodding and head shaking.
As a method in which a motion of a head is used as an input system, a method in which a position of a head is estimated by an externally-disposed sensor so as to determine a motion of the head has been disclosed. Further, a method in which an acceleration sensor is attached on a head of a user and a value obtained from the acceleration sensor is analyzed so as to determine a motion of the head has been disclosed (for example, Japanese Laid-open Patent Publication No. 2011-14082).